Lubricant additive

ABSTRACT

THIS INVENTION IS CONCERNED WITH COMPOUNDS THAT MAY BE USED AS ADDITIVES IN SYNTHETIC LUBRICANTS. THE COMPOUNDS ARE FORMED FROM AN AMIDE OF BENZOIC ACID OR A SUBSTITUTED BENZOIC ACID AND AMINOGUANIDINE BICARBONATE, AND A SALT-FORMING ALIPHATIC OR AROMATIC CARBOXYLIC ACID HAVING FROM ABOUT 6 TO 40 CARBON ATOMS.

United States Patent 3,749,702 LUBRICANT ADDITIVE Raymond H. Boehringer and Robert E. Vail, Cincinnati, Ohio, assignors to Emery Industries, Inc., Cincinnati, Ohi

0 No Drawing. Original application Aug. 14, 1968, Ser. No-

755,495. Divided and this application Mar. 31, 1971, Ser. No. 130,032

Int. Cl. C09f 1/04 U.S. Cl. 260-975 6 Claims ABSTRACT OF THE DISCLOSURE This application is a division of Ser. No. 755,495 filed Aug. 14, 1968, now Pat. No. 3,595,793.

BACKGROUND OF THE INVENTION This invention relates to metal deactivators useful as additives in lubricants and, more particularly, to salts formed from an amide prepared from benzoic acid or a substituted benzoic acid and aminoguanidine bicarbonate, and an aliphatic or aromatic carboxylic acid. The metal deactivator compounds of this invention are useful additives in synthetic ester lubricant compounds and paraffinic lubricants.

The problems that are connected with the lubrication systems of gas turbine engines and internal combustion engines have increased with the advent of more modern engines. A petroleum lubricant or a synthetic ester lubricant alone will not withstand the severe conditions that exist in these new engines. Both internal combustion and turbine engines stress lubricants and generate a series of chemical reactions that affect lubricant quality. While piston engines are usually operated under mild conditions, they are ventilated and the increased air contact causes rapid oxidative deterioration of the lubricant. When synthetic ester lubricants are used this stress causes the lubricant ester to be broken apart with primary acids and olefins being formed as the decomposition products with a consequent increase in acid value and viscosity. The metals present in the engine act as catalysts in promoting the oxidation as they are attacked by the free acid. Gas turbine engines do not have ventilated lubricating systems but they are operated at higher temperatures which cause rapid oxidation which is, like in piston engines, increased by the catalytic activity of the engine metals.

Many compounds have been added to lubricant systems in the past to decrease the oxidation of the lubricant and inhibit the catalytic activity of the engine metals. Among the compounds used are N-phenyl-alpha-naphthylamine, phenothiazine, N-butyl-p-aminophenol, 2,6 ditertbutylparacresol, and N,N-disalicylidene propylenediamine; however, these compounds are less effective at high temperatures, their use frequently being accompanied by an accumulation of an insoluble sludge in the engine.

Since these compounds either alone or in combination have not alleviated all of the problems connected with the oxidation of lubricants due to metal catalysis, a need has persisted for more eflfective metal deactivators for lubricants used in modern day engines.

It has been discovered that the compounds of the present invention have unexpectedly good metal deactivating properties. They are more effective than and overcome the problems of the commonly used metal deactivators described above. Certain of these compounds are also extremely eifective in reducing sludge accrual in lubricants.

DESCRIPTION OF THE INVENTION This invention is concerned with compounds that may be used as metal deactivator additives in engine lubricants. These compounds are salts of an amide prepared from a benzoic acid or a substituted benzoic acid and aminoguanidine bicarbonate, and a salt-forming aliphatic or aromatic carboxylic acid having from about 6 to 40 carbon atoms.

The salts of this invention are prepared by first forming intermediate amides. These amides are made from aminoguanidine bicarbonate and a benzoic acid. The benzoic acids which may be used in the preparation of the intermediate amides may have alkyl, alkenyl, halogen, or hydroxyl groups substituted for a hydrogen atom on the benzene ring. Specific examples of benzoic acids which may be used in forming the compounds of this invention are salicyclic acid, orthonitrobenzoic acid, orthochlorobenzoic acid, and benzoic acid itself.

The salt-forming carboxylic acids which may be used to make the salts constituting the invention may be chosen from aromatic or aliphatic monoor polycarboxylic acids having from about 6 to 40 carbon atoms. Representative carboxylic acids are benzoic acid, oleic acid, stearic acid, isostearic acid (described in US. Pat. No. 2,812,342), adipic acid, azelaic acid, dodecanedioic acid, and tall oil fatty acids, or other unsaturated fatty acids, such as soybean oil acids, linseed oil acids, or cottonseed oil acids. These acids may be used either alone or in combination. When the tall oil fatty acids or other unsaturated fatty acids are used, we have found that they work best when used in combination with rosin acids.

The salts of this invention are preferably made in two steps. The intermediate amide is prepared by reacting equimolar amounts of the benzoic acid and aminoguanidine bicarbonate in an alcohol medium. The solution is heated to 60 C. with constant stirring until the emission of gas ceases (about 20 minutes). The alcohol medium may be a mixture of alcohols, such as isopropanol and methanol or some alcohols, such as methanol may be used alone. When isopropanol and methanol mixtures are used, a particularly effective combination is 12% by weight isopropanol and 88% by weight methanol. The use of an alcohol such as methanol offers the advantage that after the salt is formed it may be stored in the solution for larger production and handling case. The salt-forming acid is added to the amide-alcohol solution in an equal molar amount with the amide formed in the preceeding step. The temperature of the solution is maintained at 60 C. with constant stirring. As stated above, the salt now present in the solution may be stored in a methanol solution or it may be dried. In either form the salt is stable and has a long shelf life.

The compounds of this invention are believed to conform to the following structure when a monocarboxylic acid is employed as the salt forming acid:

wherein R may be hydrogen or an alkyl, alkenyl, hydroxyl, or halogen group and X is a monocarboxylic acid radical having the formula:

l R1-CO- wherein R, is an aliphatic or aromatic radical having from about 5 to about 39 carbon atoms, and when a dicarboxylic acid is used as the salt-forming acid, the compounds of this invention are believed to conform to the following structure:

wherein R is as defined above and X has the formula:

wherein R is an alkylene radical having from about 4 to 38 carbon atoms.

A preferred salt of the present invention is prepared by reacting equimolar amounts of salicylic acid and aminoguanidine bicarbonate to form an amide and then reacting the resulting amide with an equimolar amount of tall oil acids following the procedure described above with an isopropanol/methanol solution. In the above preferred embodiment, the tall oil acids should be composed of fatty acids and rosin acids wherein the amount of rosin acid may vary from to 40 percent by weight of the total mix of tall oil acids, and preferably from to 25 percent by weight of the tall oil acids. The tall oil fatty acids are composed principally of oleic and linoleic acids with minor amounts of stearic, linolenic, and palmitic acids.

We have found that the salts prepared with dicarboxylic acids as the salt-forming acids provide lubricant additives which are particularly elfective in reducing sludge formation. The preferred dicarboxylic acid is dodecanedioic acid.

The salts of this invention may be used as metal deactivators in most if not all synthetic ester lubricants including those prepared from various combinations of aliphatic monocarboxylic acids and dicarboxylic acids having from about 6 to about 36 carbon atoms, and monohydric and polyhydric aliphatic alcohols having from about 4 to about carbon atoms. Among the ester lubricants in which the salt may be used are simple esters, such as diisooctyl azelate, di-2-ethylhexyl azelate, di-Z-ethylhexyl sebacate, di-Z-ethylhexyl adipate, dilauryl succinate, di-2-ethoxyethyl sebacate, pentaerythritol tetravalerate, di 2-ethylhexyl dimerate, and complex esters having a structural formula such as: XY-Z-Y-X, wherein X is a monohydric alcohol radical, Y is a dibasic acid radical, and Z is a glycol radical, or a structural formula such as: A--BC-BA, wherein A is a monocarboxylic acid radical, B is a glycol radical, and C is a dicarboxylic acid radical. Examples of complex esters in which the salts may be used are the reaction products of 2-ethyl-1,3- hexanediol, sebacic acid, and 2-ethylhexanoic acid; adipic acid, diethylene glycol, and Z-ethylhexanoic acid; sebacic acid, trimethylolpropane, and pelargonic acid; sebacic acid, trimethylolethane, and hexanoic acid; and sebacic acid, 1,3,5,7-octanetetraol and pentanoic acid.

The amount of the salts of this invention which may be used in lubricant base fluids varies, but generally they are used in minor amounts of from about 0.001 to about 0.5 percent by weight and preferably from 0.01 to 0.10 percent by weight based on the total weight of the lubricant composition.

Among the other additives which may be used with the salts prepared from this invention are viscosity index improvers, other antioxidants, extreme pressure agents, detergents, and pour point depressants. Examples of these additives are diphenylamine, phenyl-alpha-naphthylamine, dioctyl diphenyl amine, quinizarine, and compounds sold under the trademarks Acryloid 710 and Acryloid HP 866.

One lubricant base fluid in which the compounds of the present invention have been found to function particularly well is diisodecyl azelate.

In order to more clearly illustrate the present invention, but in no way limiting the scope thereof, the following examples are provided.

EXAMPLE I N-guanidinosalicylarnide, an intermediate compound in the preparation of salts of this invention, was prepared by reacting 136.8 gms. of aminoguanidine bicarbonate with 138 gms. of salicylic acid in 400 ml. of an alcohol mixture (12% isopropanol and 88% methanol). The mixture was stirred for 15 minutes without heat and then for thirty minutes at a constant temperature of 60 C. The reaction mixture was then placed in a 3 neck 500 ml. flask and the alcohol was removed using agitation, heat, and vacuum, leaving the N-guanidinosalicylamide product.

EXAMPLE II Another intermediate was prepared following the procedure in Example I but substituting 122.1 gms. of benzoic acid for the salicylic acid. The product, N-guanidinobenzamide, was recovered and retained for use in preparation of a salt.

EXAMPLE III A salt was prepared by adding 50 gms. of the N-guanidinosalicylamide prepared in Example 1 to 300 ml. of methanol and 72.3 gms. of tall oil acids, a mixture of fatty acids and rosin acids. The fatty acid portion of the tall oil acidwas composed of acids having 14 to 18 carbon atoms, about 50 percent of the acids being unsaturated. The fatty acids comprised percent by weight of the acid mixture. The remaining acids are primarily resin acids of the abietic and pimaric types having a phenanthrene nucleus. They are unsaturated and hence reactive. An unsaponifiable portion of this resin (3-10%) contains hydrocarbons and high molecular weight alcohols. After stirring for 15 minutes the alcohol solution of amide and acids was distilled in a 3 neck 500 ml. flask with stirring, heat, and vacuum. When the temperature reached C., the product was discharged.

EXAMPLE IV A salt was formed following the same procedure described in Example III except that 42.1 gms. of dodecanedioic acid were substituted for the tall oil acids.

EXAMPLE V A salt was formed following the procedure in Example III except that 106.0 gms. of dimer acid, a polymerized oleic acid, sold under the trademark Empol 1016, were substituted for the tall oil acids.

EXAMPLE VI A salt was formed following the procedure in Example III except that 55.4 gms. of the intermediate prepared in Example II were substituted for the N-guanidinosalicylamide.

EXAMPLE VII A salt was prepared following the procedure in Example 11 except that 82.7 gms. of isostearic acid, a modified fatty acid described in US. Pat. No. 2,812,342, were substituted for the tall oil acids.

EXAMPLE VIII A salt was prepared following the procedure set forth In Example III except that 72.2 gms. of oleic acid were substituted for the tall oil acids.

EXAMPLES IX-XXIV Each of the salts prepared in Examples III to VIII was compounded in synthetic ester lubricant base fluids along with other conventional lubricant additives. The compositions of these fluids are shown below in Table I. For comparative purposes, two synthetic lubricant compositions shown in Examples XXII and XXIII were prepared without the salts of this invention. A commercial metal deactivator, benzotriazole, was used in place of a salt of the present invention in Example XXIV for comparative purposes.

Examples XVII and XIX to XXI in Table I were evaluated by using Federal Test 791, method 5308, at several temperatures. The results of these tests showed the compounded lubricants to have good oxidation stability, slight effect on the metals and low sludge content. Based upon these results, the lubricants are satisfactory for use in diesel engines.

TABLE I Example IX Basefluid:

Pentaerythrltolester 94.93 93.73 93.13 93.73 94.93 94.93 Diisodecyl Ditridecyl MAMA Diocty} 0701000 1276-65R 3 Di-2-ethylhexy1 mlipatn Di-Z-ethylhexyl dodecane- 11mm Emery 3383 3 TMP (1210):

AddIi%iIves.Salt of Example:

X XI XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII XXIV 93.94 22.00 III V VI. VII VIII Commercial metal deactivator (Benzotrazole) Commercialantioxidant 2.00 2.00 2.00 2.00 2.00 2.00 Commercial thickener 1.2 1.2 1.2 Commercial detergent (Juinimrin 0.02 'ICP 3.00 3.00 3.00 3.00 3.00 3.00

Azelaic.

2.00 2.00 2.00 2.00 ZiOg 2.00

1 An ester of monopentaerythritol and a mixture of C to C aliphatic monobasic acids.

2 An ester of technical grade pentaerythritol [12% diand 88% moncpentaerythritol] and a mixture of C to Ca aliphatic monobaslc acids. 3 Au ester of trimethylol propane and a mixture of C to C aliphatic mouobasic acids. 4 1210 is a mixture of C0, C1, and Ca monobasic acids which have an average carbon atom content of 7.

The lubricant compositions prepared above were evalunot lowered sufliciently to meet the specifications of PWA ated for oxidation stability using Federal Test 791, Cor- 52143; however, the Specification of PWA 52143 can be rosion and Oxidation Stability, method 5308, as modified by Pratt and Whitney specifications described in PWA 521-B.

easily met by using a commercial thickener as was done in Examples X to XII.

TABLE II Example IX X XI XII XIII XIV XV XVI XVIII XXII XXIII XXIV Viscosity change at 100 F 71. 70 48. 9 46. 2 48. 6 59. 1 69. 7 56. 7 69. 7 71. 8 80. 8 81. 3 84. 6 Copper corrosion (mgJcmfl). 0. 220 0. 09 0. 07 0. 08 0. 285 0. 238 0. 161 0. 238 0. 146 1. 070 1.32 0. 86 Steel corrosion (mg./cm. 0. 008 +0. 05 +0. 06 0. 02 +0. 015 --0. 092 0. 015 0. 092 +0. 023 0 +0.05 +0. 02 Silver corrosion (mg/0111. 0.254 0.02 0.05 +0.02 0. 269 0. 238 0. 208 0. 238 +0. 062 0. 238 0. 01 .02 Aluminum corrosion (mg/ch11). 0. 023 0. 01 0 +0. 01 0. 061 0. 069 0. 06 0. 068 -0. 010 0. 03 0. 02 Magnesium corrosion (mgJcmfi). 0. 254 0. 28 0. 07 0. 19 1. 046 0. 246 0. 142 0. 246 0. 020 1. 575 0. 15 2. 26 Sludge (mg.) 60. 6 9. 5 105 26. 0 153. 1 49. 4 36. 8 49.4 39. 8 161 l Unfilterable.

The oxidation stability test, described in Federal Test 791, method 5308, is performed by heating an aerated lubricant with five metal coupons present in the fluid. These metals are copper, steel, aluminum, magnesium and silver. This test is conducted at a temperature of 425 F. instead of the usual 347 F. for 72 hours. At the end Off this period each metal weight must not have changed by more than $0.30 mg./cm. and the viscosity of the fluid should not have increased by more than percent.

The results of the tests performed on the compositions of Table I are provided in Table II. These results show that the salts of Examples III to IV and VIII when used in lubricant compositions IX to XII and XIV to XVI effectively inhibited metal loss to well within the tolerable limits; whereas, in comparative Examples XXII and XXIII which did not have a metal deactivator of this invention added, the copper and magnesium losses were far in excess of tolerable levels. It may also be seen that in comparison with the commercial metal deactivator used in composition Obviously, many modifications and variations of this invention may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A composition of matter useful as an additive in synthetic lubricants comprising the reaction product of (a) an amide formed from (1) an acid selected ctrom the group consisting of benzoic acid, alkyl-substituted benzoic acid, alkenyl-substituted benzoic acid, halogen-substituted benzoic acid, hydroxyl-substituted benzoic acid and mixtures thereof and (2) aminoguanidine bicarbonate; and

(b) a salt-forming aliphatic or aromatic acid having from about 6-40 carbon atoms.

2. The composition of claim 1 wherein (l) is selected from the group consisting of benzoic acid, salicylic acid, orthonitrobenzoic acid,'and orthochlorobenzoic acid.

3. The composition of claim 1 wherein said salt-forming acid (b) is a monocarboxylic acid.

4. The composition of claim 1 wherein said salt-forming acid (b) is a tall oil acid.

5. The composition of claim 1 wherein said salt-forming acid (b) is a dicarboxylic acid.

6. The composition of matter of claim 1 wherein (1) is selected from the group consisting of benzoic acid, salicylic acid, orthonitrobenzoic acid and orthochlorobenzoic acid, (1) and (2) are reacted in equimolar amounts and the salt-forming acid (b) is selected from the group consisting of benzoic acid, oleic acid, stearic acid, isostearic acid, adipic acid, azelaic acid, dodecanedioic acid, tall oil acids, soybean oil acids, linseed oil acids, and cottonseed oil acids.

References Cited UNITED STATES PATENTS 2,677,700 5/1954 Jackson 26097.5 2,911,368 11/1959 Fowler 252-34 2,522,312 9/1950 Smith 25250 MAURICE J. WELSH, Primary Examiner W. E. PARKER, Assistant Examiner US. Cl. X.R. 

